When G. S. Phalen introduced a contemporary investigation of "Spontaneous Compression of the Median Nerve of the Wrist" at the 99th annual meeting of the American Medical Association few people considered the matter of great importance. Today the "spontaneous compression" is recognized as Carpal Tunnel Syndrome and has become the most prevalent cumulative trauma disorder reported in the workplace. The proliferation of articles has made carpal tunnel syndrome a household word creating increased public concern but there remain only a few options for treatment.
The exact mechanical basis for carpal tunnel syndrome varies among authors, but the basic premise is consistent. The carpal tunnel is a relatively fixed structure through which several tendons and the median nerve, the main nerve for the fingers, travel. When swelling or inflammation of the tissues occurs the median nerve is pinched creating the signs and symptoms of carpal tunnel syndrome.
Symptoms are believed to be caused by factors which increase the size of the tissues within the carpal tunnel, an abnormal condition which narrows the tunnel, or posterior sympathetic cervical stress syndrome. The latter syndrome is characterized by irritation of the lower four cervical nerve roots, which contain preganglionic sympathetic fibers. In this condition, however, pain is usually exhibited in the entire hand instead of only in the median nerve distribution.
Prior to the onset of acute symptoms muscle weakness or paresthesia is often experienced. Patients will often complain of cutaneous sensory irritation characterized by numbness, burning, or tingling in the first three fingers and the radial half of the ring finger, but usually not the fifth digit. When the patient says that his or her hand feels numb, it usually indicates motor impairment, not sensory. In addition, there can be impairment in the ability to sense heat and cold, fine tactile discrimination, and pain, since the median nerve carries most of the sympathetic nerve supply to the hand.
The pain can occur during daily activities, nocturnally, or upon awakening. Nocturnal pain in the median nerve distribution of the hand is considered to be pathognomonic for carpal tunnel syndrome. This pain can usually be relieved by shaking or rubbing the hand or arm or immersing the affected limb in warm water. The acute attack usually subsides within a few minutes to an hour.
Referred pain has been documented to radiate up into the forearm, elbow, and shoulder, thus mimicking a myriad of other syndromes. The patient may also complain of motor involvement characterized by difficulty in holding a pencil, opening a jar or dropping objects for no apparent reason. The contribution of occupational factors is often overlooked, despite recent research indicating that up to 47% of all cases of carpal tunnel syndrome may be caused by workplace factors.
The carpal tunnel is an osseofibrous structure formed by the flexor retinaculum and the anterior surfaces of the proximal and distal rows of the carpal bones. From medial to lateral the proximal bones are pisiform, triquetrum, lunate and scaphoid. From medial to lateral the distal bones are hamate, capitate, trapezoid and trapezium. The flexor retinaculum is also known as the transverse carpal ligament, the annular ligament, the anterior annular ligament or the deep transverse carpal ligament. The flexor retinaculum is the size of a "postage stamp" with two surfaces and four borders.
The landmark for the proximal border of the flexor retinaculum is the distal crease at the wrist. The anterior surface of the flexor retinaculum is the origin of the thenar and hypothenar muscle groups responsible for the opposition of digits and pinch strength. The dorsal surface of the flexor retinaculum is associated with the contents of the carpal tunnel containing:
1) nine tendons (4 superficial, 4 deep, 1 pollicis longus) PA1 2) one median nerve PA1 3) two bursae (ulnar and radial)
The median nerve lies in front of the bursae of the flexor tendons and close to the dorsal surface of the flexor retinaculum. The function of the flexor retinaculum is to retain the long flexor tendons close to the skeleton so that the tendons do not spring away from each joint as it is flexed. The fibrous retinaculum increases the strength of the carpus and the efficiency of the muscles. The actual borders of the flexor retinaculum traverse from the medial (hypothenar) attachment on the pisiform and hamulus of the hamate to the lateral (thenar) attachment at the tubercle of the navicular (scaphoid) and the tubercular ridge of the greater multangular (trapezium).
The current protocol for conservative treatment focuses on splinting. The basis for this approach comes from findings that patients exhibiting carpal tunnel syndrome had elevated resting intracanal pressure. Wrist flexion and extension studies have demonstrated that the intracanal pressure increases from three to six times that found in the neutral position. Extension resulted in somewhat greater increases than flexion, especially in the distal aspect of the tunnel. Immobilizing the wrist in a neutral position is the popular treatment. Steroid injection is the drug therapy of choice but, due to the potential danger of chemical neuritis or aseptic necrosis, its value is limited to three or four administrations.
The final step in treating carpal tunnel syndrome has been decompression of the carpal tunnel by transecting the flexor retincaculum. A number of authorities indicate the long term effects do not substantiate the decompression theory. Despite its high incidence and its reputation for simplicity and efficiency, carpal tunnel release does not invariably produce good results, and dissatisfied patients are not infrequently encountered. Unsatisfactory results are caused by inaccurate diagnosis and all too frequently, iatrogenic surgical complications. The Journal of the American Medical Association reports that the initial relief provided by carpal tunnel surgery may be shadowed by significant scar pain and weakness in almost a third of the subjects after two years. The surgery, in which the carpal tunnel is decompressed by release of the transverse ligament and debridement, is the most common surgery in the workers' compensation population.
The published results of neutral splinting cites 67% of the subjects reporting symptom relief after splint use. One of the problems with this protocol is the bulky bracing which produces gross restriction at the radio-carpal joint which is proximal to the actual carpal tunnel. Significantly higher success rates were reported by using lightweight functional design splints which could be worn full time and which minimally restrict function. Various types of splinting, bracing, shock absorbing, and padding are disclosed in the patent references discussed below.
U.S. Pat. No. 4,883,073 (Aziz) discloses a wrist splint with integral elements for reducing aggravation of the median nerve by maintaining the wrist in a neutral unflexed position. The wrist movement is considerably restricted. U.S. Pat. No. 5,014,689 (Meunchen, et al.) describes a brace for the hand that limits hand extension and flexion as well as ulnar and radial deviation. U.S. Pat. No. 4,899,763 (Sebastian, et al.) describes a therapeutic appliance for the wrist and lower forearm having inflatable chambers and an elastic loop or strap wrapped around the thumb for immobilizing the wrist and acting as a means for preventing injury to the neural, tendinous and ligamentous tissues. These three devices are designed specifically to restrict the motion of the hand and wrist, and as such would have little value or utility to an individual who must return to the workplace or desires to pursue normal daily routines.
Another group of patent references describes gloves or other related devices that shield the section of the hand and/or wrist where median nerve exposure is greatest. These devices protect against impact by cushioning, but do not act to relieve median nerve pressure nor the pain from carpal tunnel syndrome. U.S. Pat. No. 5,031,640 (Spitzer) describes a contoured pad for tool handles and the like such that the median nerve is protected during the gripping process. U.S. Pat. No. 4,905,321 (Walunga) describes a sports glove that combines hand protection and an attached wrist strap for supporting wrist tendons during lifting of heavy weights. U.S. Pat. No. 4,561,122 (Stanley, et al.) discloses a glove with shock absorbing padding designed to maintain a palmar/dorsal balance of sensation to retain cognizance by touch for baseball players.
U.S. Pat. No. 4,958,384 (McCrane) describes a safety glove with a stiffening rib built into the back or non-palmar side, and an elastic strip that can be wrapped around the wrist area more than one time in an attempt to prevent hyperextension in sports or work activities. U.S. Pat. No. 4,850,341 (Fabry, et al.) describes a glove for inhibiting carpal tunnel syndrome pain by using a pad to protect the median nerve from vibration and shock. U.S. Pat. No. 4,531,241 (Berger) describes a glove for use in protecting hands from impact machinery (jack hammer, rivet guns, etc.) with a cushioning pad on both the outside and inside of the palmar side is used with the pads extending down and over the wrist.
In certain cases thumb injuries can be associated with carpal tunnel syndrome and the following patent references are concerned with protection or immobilizing the thumbs, but do not address the carpal tunnel syndrome problem. U.S. Pat. No. 4,565,195 (Eisenberg) describes a glove with a retainer to restrict the motion of the thumb if it is bent abnormally. U.S. Pat. No. 4,658,441 (Smith) describes a one piece thumb support that covers the thumb/index finger web. U.S. Pat. No. 4,935,568 (Theisler) describes a flexible, adjustable thumb brace that restricts the motions of the thumb and is specific to protecting an injured thumb.
None of the foregoing patents addresses relief of pressure on the median nerve or protection/alleviation of the pain from carpal tunnel syndrome. However, one patent reference does suggest the use of compressive forces over the wrist area of the forearm to relieve carpal tunnel stress.
U.S. Pat. No. 4,966,137 (Davini) discloses the use of a semi-rigid plastic clamp with open ends that is molded in place over a patient's wrist. The open ends of the clamp are curved inwardly, and are placed over the location of the median nerve in the wrist. An overwrap elastic bandage is used to pull the clamp ends together and produce compressive forces on the radius and ulna bones which, in turn produces a decompression effect on the median nerve and claims some expansion of the carpal tunnel. The limitations of this device are: (a) position of application is proximal to the anatomical structures comprising carpal tunnel and only a minor carpal tunnel enlargement can be achieved without causing patient discomfort and skin trauma; (b) removal, adjustment, and replacement must be carried out by a medical professional; and (c) non-porosity and bulk of the device will likely exacerbate contact dermatritis or dermative sensitivity. As in the cases of the patent references discussed above, this reference does not address alleviation of pain or remedial effects for carpal tunnel syndrome accomplished by the present invention through the use of compressive inwardly directed force over the metacarpal-phalangal region as more fully described below.
As surgical intervention should be the last choice in treatment for any condition, including carpal tunnel syndrome, the usual regimen utilizes various types of braces, splints and medications. Although functional, these devices are often bulky and uncomfortable. Further, their utility resides in limiting the degree of motion of a patient's hand and wrist to alleviate median nerve pain and additional irritation. These motion restrictions prevent a patient from returning to the workplace in a fully productive condition as well as significantly inhibiting the performance of normal daily personal routines.
It is not unreasonable to state that these splints and braces require a change in life style for a person afflicted with carpal tunnel syndrome. The importance of the above factors is highlighted by the fact that the Occupational Safety and Health Agency, a federal regulatory agency, no longer permits workers to return to their jobs if splints are used in the treating of carpal tunnel syndrome. The corresponding loss of productivity plus insurance and other related health care costs represent significant economic burdens on both workers and industries.
The present invention, hereinafter sometimes referred to as the Carpal Tunnel Mitt or CTM, obviates the limitations described above, and provides a unique new approach to the conservative treatment of carpal tunnel syndrome. A review of the technical literature, commercially available products, and patent references have not disclosed the use of any similar designs or utility. The Carpal Tunnel Mitt has taken the optimal aspects of functional anatomy and blended the desire for a lightweight functional splint that can be worn full time. The mechanism that makes the Carpal Tunnel Mitt unique is approximating the borders of the flexor retinaculum without muscle contraction and inhibiting only the very end stages of wrist flexion and extension to reduce the stressors at the carpal tunnel. The mechanical opposition of the 1st to the 5th metacarpal-phalangal region deepens the carpal tunnel allowing for natural decompression forces on the structures within the carpal tunnel. It also provides maximum space at the distal aspect of the carpal tunnel where the highest incidence of impaired sensory conduction of the median nerve is seen. This is distal to any actual flexion-extension mechanics which occur at the radio-carpal and mid-carpal region.
Application of the Carpal Tunnel Mitt is corrective, rehabilitative and preventative spanning all occupations where repetitive strain injuries exist. The CTM provides relief in acute and chronic cases and may become essential in management of the Double Crush Syndrome. Some carpal tunnel symptoms have been attributed to cervical nerve root compression when seen during waking hours versus nocturnal onset. This expanded view of cervical interaction is best managed through Chiropractic care or practitioners of manual medicine in conjunction with application of the Carpal Tunnel Mitt which will provide the maximum opportunity for conservative management and relief of the signs and symptoms of carpal tunnel syndrome, thus reducing the need for drug therapy and surgery.
It is, therefore, an object of the present invention to provide a means for non-invasive relief from the pains associated with carpal tunnel syndrome having only minimal restrictions of hand and wrist motions.
A further object of the invention is to provide a lightweight flexible apparatus made of porous, stretchable fabric that allows the skin to breathe while it is being worn.
Another object of the invention is to provide a means for orienting a tensioning device to retain the bones and associated ligaments of the carpal tunnel in a fixed position while the invention is in place and thereby relieve the pressure on the median nerve during various manual activities.
A still further object of this invention is the enlargement of the dimensions of the carpal tunnel by the application of natural decompression forces effectuated by the mechanical deepening of the carpal tunnel by allowing the flexor retinaculum to contract by holding the proximal bones of the hand in a fixed spaced relationship.
Relief of the pressure on the median nerve and other components of the carpal tunnel and subsequent self-healing are directly related to the degree of the carpal tunnel enlargement. The decompression is effected by the displacement of the tendons, bursae and median nerve which return to their normal location when decompression is terminated.
An additional object of the present invention is that it can be used advantageously in combinations with or attached to splints of various types for those treatments in which it is medically necessary to support and/or immobilize the wrist and/or forearm area.
For example the CTM can be used in conjunction with the Sebastian therapeutic appliance or the Aziz remedial device. These examples are illustrative and should not be considered as a limitation. Additionally, the CTM could be consolidated with various safety or sports glove designs; for example with Stanley, et al. and McCrane, or any of the currently available commercial gloves. Again, these examples are illustrative and should not be considered as a limitation on the scope of the invention.
Other objects will appear hereinafter.